/**
* Copyright (c) 2013, Institute of Information Systems (Sven Groppe and contributors of LUPOSDATE), University of Luebeck
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
* following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this list of conditions and the following
* disclaimer.
* - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
* following disclaimer in the documentation and/or other materials provided with the distribution.
* - Neither the name of the University of Luebeck nor the names of its contributors may be used to endorse or promote
* products derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package lupos.optimizations.logical.rules.rdfs;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import lupos.datastructures.items.Variable;
import lupos.engine.operators.BasicOperator;
import lupos.engine.operators.OperatorIDTuple;
import lupos.engine.operators.messages.BoundVariablesMessage;
import lupos.engine.operators.multiinput.join.Join;
import lupos.engine.operators.singleinput.Projection;
import lupos.engine.operators.singleinput.ReplaceVar;
import lupos.misc.Tuple;
import lupos.optimizations.logical.rules.Rule;
public class RuleReplaceVarUnderJoin extends Rule {
@Override
protected void init() {
final Join join = new Join();
final ReplaceVar replaceVar = new ReplaceVar();
join.setSucceedingOperator(new OperatorIDTuple(replaceVar, 0));
replaceVar.setPrecedingOperator(join);
subGraphMap = new HashMap<BasicOperator, String>();
subGraphMap.put(join, "join");
subGraphMap.put(replaceVar, "replaceVar");
startNode = join;
}
@Override
protected boolean checkPrecondition(final Map<String, BasicOperator> mso) {
final Join join = (Join) mso.get("join");
final ReplaceVar replaceVar = (ReplaceVar) mso.get("replaceVar");
final LinkedList<Variable> replaceRightVars = replaceVar
.getSubstitutionsVariableRight();
final Object[] joinVars = join.getIntersectionVariables().toArray();
// Only interesting if minimum one right ReduceEnv-Variable is not join
// partner
for (int i = 0; i < replaceRightVars.size(); i++) {
if (!arrayContains(joinVars, replaceRightVars.get(i))) {
// Because of complexity transform only joins which have only
// the ReplaceVar as successor
if (join.getSucceedingOperators().size() == 1) {
return true;
}
}
}
return false;
}
private ReplaceVar getReplaceAfterPre(final ReplaceVar replaceVar,
final ReplaceVar originalClone, final BasicOperator pre,
final Join join) {
final ReplaceVar replaceAfterPre = new ReplaceVar();
final Object[] unionPre = pre.getUnionVariables().toArray();
final LinkedList<Variable> replaceVarsLeft = originalClone
.getSubstitutionsVariableLeft();
final LinkedList<Variable> replaceVarsRight = originalClone
.getSubstitutionsVariableRight();
final Object[] intersectionJoin = join.getIntersectionVariables()
.toArray();
for (int i = 0; i < replaceVarsLeft.size(); i++) {
final Variable replaceVarRight = replaceVarsRight.get(i);
final Variable replaceVarLeft = replaceVarsLeft.get(i);
// Join gets (p,lit1) (p,lit2) and ReplaceVar has (x,p) => no
// trigger
// After incorrect Transformation Join could get (x,lit1) (p,lit2)
// => trigger
if (!arrayContains(intersectionJoin, replaceVarRight)) {
// Right variable be replaced over join
if (arrayContains(unionPre, replaceVarRight)) {
replaceAfterPre.addSubstitution(replaceVarLeft,
replaceVarRight);
replaceVar.removeSubstitutionVars(i);
}
}
}
return replaceAfterPre;
}
private Projection getProjectionAfterReplace(final ReplaceVar replacePre,
final BasicOperator pre) {
final Projection projectionPre = new Projection();
final Object[] unionVars = pre.getUnionVariables().toArray();
final LinkedList<Variable> replaceVarsLeft = replacePre
.getSubstitutionsVariableLeft();
final LinkedList<Variable> replaceVarsRight = replacePre
.getSubstitutionsVariableRight();
// Let the tupel from the new ReplaceVar through
for (int i = 0; i < replaceVarsLeft.size(); i++) {
projectionPre.addProjectionElement(replaceVarsLeft.get(i));
}
// Let all UNION-Variable through, but not the ones which the new
// ReplaceVar has replaced (right side)
final LinkedList<Variable> projVars = new LinkedList<Variable>();
for (int i = 0; i < unionVars.length; i++) {
final Variable var = (Variable) unionVars[i];
if (!replaceVarsRight.contains(var)) {
projVars.add(var);
}
}
// Add the calculated variables to the new projection
for (int i = 0; i < projVars.size(); i++) {
projectionPre.addProjectionElement(projVars.get(i));
}
return projectionPre;
}
@Override
public Tuple<Collection<BasicOperator>, Collection<BasicOperator>> transformOperatorGraph(
final Map<String, BasicOperator> mso,
final BasicOperator rootOperator) {
final Collection<BasicOperator> deleted = new LinkedList<BasicOperator>();
final Collection<BasicOperator> added = new LinkedList<BasicOperator>();
final Join join = (Join) mso.get("join");
final ReplaceVar replaceVar = (ReplaceVar) mso.get("replaceVar");
// Generate a clone
final ReplaceVar originalClone = new ReplaceVar();
originalClone.setSubstitutionsVariableLeft(replaceVar
.getSubstitutionsVariableLeft());
originalClone.setSubstitutionsVariableRight(replaceVar
.getSubstitutionsVariableRight());
final LinkedList<BasicOperator> pres = (LinkedList<BasicOperator>) join
.getPrecedingOperators();
BasicOperator pre;
final LinkedList<Integer> indices = new LinkedList<Integer>();
// Remark the operator-IDs of the precessors
for (int i = 0; i < pres.size(); i++) {
pre = pres.get(i);
indices.add(pre.getOperatorIDTuple(join).getId());
}
ReplaceVar rep;
Projection projectionPre;
for (int i = 0; i < pres.size(); i++) {
pre = pres.get(i);
// Calculate the new ReplaceVar which will be replaced between the
// i-th precessor and the join
rep = getReplaceAfterPre(replaceVar, originalClone, pre, join);
// Calculate projection after precessor and new ReplaceVar
projectionPre = getProjectionAfterReplace(rep, pre);
added.add(rep);
added.add(projectionPre);
pre.setSucceedingOperator(new OperatorIDTuple(rep, 0));
rep.setPrecedingOperator(pre);
rep.setSucceedingOperator(new OperatorIDTuple(projectionPre, 0));
projectionPre.setPrecedingOperator(rep);
projectionPre.setSucceedingOperator(new OperatorIDTuple(join,
indices.get(i)));
join.setPrecedingOperator(projectionPre);
}
rootOperator.deleteParents();
rootOperator.setParents();
rootOperator.detectCycles();
rootOperator.sendMessage(new BoundVariablesMessage());
if (deleted.size() > 0 || added.size() > 0)
return new Tuple<Collection<BasicOperator>, Collection<BasicOperator>>(
added, deleted);
else
return null;
}
private boolean arrayContains(final Object[] vars, final Variable var) {
for (int i = 0; i < vars.length; i++) {
if (vars[i].equals(var))
return true;
}
return false;
}
}